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SIMULATION OF hot forming PROCESSION IN Mn18Cr18NSTEEL

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Acta Metallurgica Sinica(English Letters) 2000年第2期13卷 434-438页

作者： M. Guan, J. L. song and H. G. Guo Taiyuan Heavy Machinery Institute, Taiyuan 030024, China

In the hot forming of Mn18Cr18N steel, such problems as easy cracking, difficult controlling of forming paramenters often occur. In this paper,the variation rule of the plasticity of the steel, the starting mechanism of micro-crack and its generating characteristics were studied with the combination of thermodynamic simulation test, micro-simulation and FEM, the related data of microstructure change and hot forming parameters were produced. The hot forming process of 600MW generator retaining ring was analyzed as an example.

关键词： Mn18Cr18N hot forming FEM numerical simulation

Application of hot forming High Strength Steel Parts on Car Body in Side Impact

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Chinese Journal of Mechanical Engineering 2010年第2期23卷 252-256页

作者： SUN Hongtu HU Ping MA Ning SHEN Guozhe LIU Bo ZHOU Dinglu State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian 116024 China School of Automotive Engineering Dalian University of Technology Dalian 116024 China Academy of Changan Automotive Engineering Chongqing 401120 China

Lightweight structure is an important method to increase vehicle fuel efficiency. High strength steel is applied for replacing mild steel in automotive structures to decrease thickness of parts for lightweight. However, the lightweight structures must show the improved capability for structural rigidity and crash energy absorption. Advanced high strength steels are attractive materials to achieve higher strength for energy absorption and reduce weight of vehicles. Currently, many research works focus on component level axial crash testing and simulation of high strength steels. However, the effects of high strength steel parts to the impact of auto body are not considered. The goal of this research is to study the application of hot forming high strength steel（HFHSS） in order to evaluate the potential using in vehicle design for lightweight and passive safety. The performance of HFHSS is investigated by using both experimental and analytical techniques. In particular, the focus is on HFHSS which may have potential to enhance the passive safety for lightweight auto body. Automotive components made of HFHSS and general high strength steel（GHSS） are considered in this study. The material characterization of HFHSS is carried out through material experiments. The finite element method, in conjunction with the validated model is used to simulate the side impact of a car with GHSS and HFHSS parts according to China New Car Assessment Programme（C-NCAP） crash test. The deformation and acceleration characteristics of car body are analyzed and the injuries of an occupant are calculated. The results from the simulation analyses of HFHSS are compared with those of GHSS. The comparison indicates that the HFHSS parts on car body enhance the passive safety for the lightweight car body in side impact. Parts of HFHSS reduce weight of vehicle through thinner thickness offering higher strength of parts. Passive safety of lightweight car body is improved through reduction of crash defor

关键词： hot forming high strength steel lightweight side impact car body

Influence of process parameters on properties of AA6082 in hot forming process

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Transactions of Nonferrous Metals Society of China 2017年第11期27卷 2454-2463页

作者： Wen-yu MA Bao-yu WANG Jian-guo LIN Xue-feng TANG School of Mechanical Engineering University of Science and Technology Beijing Beijing 100083 China Department of Mechanical Engineering Imperial College London London SW7 2AZ UK

The influences of process parameters on mechanical properties of AA6082in the hot forming and cold-die quenching(HFQ)process were analysed *** electron microscopy was used to observe the precipitate distribution and to thus clarify strengthening mechanism.A new model was established to describe the strengthening of AA6082by HFQ process in this novel forming *** material constants in the model were determined using a genetic algorithm *** strengthening model for AA6082can precisely describe the relationship between the strengths of formed workpieces and process *** predicted results agree well with the experimental *** Pearson correlation coefficient,average absolute relative error,and root-mean-square error between the calculated and experimental hardness values are0.99402,2.0054%,and2.045,*** model is further developed into an FE code ABAQUS via VUMAT to predict the mechanical property variation of a hot-stamped cup in various ageing conditions.

关键词： aluminium alloy AA6082 mechanical properties strengthening model hot forming

Influence of hot Press forming Techniques on Properties of Vehicle High Strength Steels

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Journal of Iron and Steel Research International 2011年第5期18卷 59-63页

作者： CHANG Ying MENG Zhao-huan YING Liang LI Xiao-dong MA Ning HU Ping School of Automotive Engineering State Key Laboratory of Structural Analysis for Industrial EquipmentDalian University of TechnologyDalian 116024LiaoningChina

Based on the combination of materials science and mechanical engineering,hot press forming process of the vehicle high strength steels was analyzed. The hot forming process included：heating alloys rapidly to austenite microstructures,stamping and cooling timely,maintaining pressure and quenching. The results showed that most of austenite microstructure was changed into uniform martensite by the hot press forming while the samples were heated at 900 ℃ and quenched. The optimal tensile strength and yield strength were up to 1530 MPa and 1000 MPa,respectively,and the shape deformation reached about 23%. And springback defect did not happen in the samples.

关键词： high strength steel lightweight hot forming martensite

Research on technological parameters of pressure forming with hot granule medium on AA7075 sheet

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Journal of Central South University 2016年第4期23卷 765-777页

作者：董国疆赵长财赵建培押媛媛曹秒艳 College of Vehicles and Energy Yanshan University Key Laboratory of Advanced Forging & Stamping Technology and Science of Ministry of Education (Yanshan University)

hot granule medium pressure forming （HGMF） process is a new process in which granule medium replaces the medium in existing flexible-die hot forming process, such as liquids, gases or viscous medium. hot forming of light alloy sheet parts can be realized based on the properties of granule medium, such as withstanding high temperature and pressure, filling well, sealing and loading easily. In this work, the forming of AA7075 cylindrical parts by HGMF process is taken as an example to establish the constitutive relation and forming limit diagram （FLD） of AA7075 sheet which is related to temperature by hot uniaxial tensile test of sheet metal. Based on the assumption that granule medium is applied to extended Drucker-Prager linear material model, the finite element model of HGMF process is established and the effect of technological parameters, such as forming temperature, blank-holder gap and drawing ratio, on the sheet metal formability, is studied. The limit drawing ratio curve of AA7075 cylindrical parts at forming temperature of 175-300 ℃ is obtained by HGMF process test, and the limit drawing ratio reaches the maximum value of 1.71 at 250 ℃. The results of numerical simulation are consistent with the results of process test, and the forming force, distribution of wall thichness and form of instability are predicted correctly, which provides reference for the application of HGMF process.

关键词： granule medium aluminum alloy sheet drawing hot forming forming limit diagram

Stress-strain analysis on AA7075 cylindrical parts during hot granule medium pressure forming

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Journal of Central South University 2016年第11期23卷 2845-2857页

作者：董国疆杨卓云赵建培赵长财曹秒艳 College of Vehicles and Energy Yanshan University Qinhuangdao 066004 China Key Laboratory of Advanced Forging & Stamping Technology and Science of Ministry of Education of China (Yanshan University) Qinhuangdao 066004 China National Engineering Research Center for Equipment and Technology of Cold Strip Rolling Yanshan University Qinhuangdao 066004 China

hot granule medium pressure forming(HGMF) is a technology in which heat-resistant granules are used to replace liquids or gases in existing flexible-die forming technology as pressure-transfer medium. Considering the characteristic of granule medium that seals and loads easily, the technology provides a new method to realize the hot deep-drawing forming on high strength aluminum alloy sheet. Based on the pressure-transfer performance test of granule medium and the material performance test of AA7075-T6 sheet, plastic mechanics analysis is conducted for the areas, such as the flange area, force-transfer area and free deforming area, of cylindrical parts deep-drawn by HGMF technology, and the function relation of forming pressure is obtained under the condition of nonuniform distribution of internal pressure. The comparison between theoretical result and experimental data shows that larger deviation occurs in the middle and later period of forming process, and the maximum theoretical forming force is less than the experimental value by 24.6%. The variation tendency of the theoretical thickness curve is close to the practical situation, and the theoretical value basically agrees well with experimental value in the flange area and the top area of spherical cap which is in the free deforming area.

关键词： granule medium aluminum alloy sheet deep-drawing hot forming limit drawing ratio

hot Granules Medium Pressure forming Process of AA7075 Conical Parts

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Chinese Journal of Mechanical Engineering 2015年第3期28卷 580-591页

作者： DONG Guojiang ZHAO Changcai PENG Yaxin LI Ying College of Vehicles and Energy Yanshan University Key Laboratory of Advanced Forging & Stamping Technology and Science of Ministry of Education Yanshan University

High strength aluminum alloy plate has a low elongation at room temperature, which leads to the forming of its components need a high temperature. Liquid or gas is used as the pressure-transfer medium in the existing flexible mould forming process, the heat resistance of the medium and pressurizing device makes the application of aluminum alloy plate thermoforming restricted. To solve this problem, the existing medium is replaced by the heat-resisting solid granules and the general pressure equipments are applied. Based on the pressure-transfer performance test of the solid granules medium, the feasibility that the assumption of the extended Drucker-Prager linear model can be used in the finite element analysis is proved. The constitutive equation, the yield function and the theoretical forming limit diagram（FLD） of AA7075 sheet are established. Through the finite element numerical simulation of hot granules medium pressure forming（HGMF） process, not only the influence laws of the process parameters, such as forming temperature, the blank-holder gap and the diameter of the slab, on sheet metal forming performance are discussed, but also the broken area of the forming process is analyzed and predicted, which are coincided with the technological test. The conical part whose half cone angle is 15° and relative height H/d0 is 0.57, is formed in one process at 250℃. The HGMF process solves the problems of loading and seal in the existing flexible mould forming process and provides a novel technology for thermoforming of light alloy plate, such as magnesium alloy, aluminium alloy and titanium alloy.

关键词： granules medium aluminum alloy sheet drawing hot forming forming limit diagram

PREDICTION OF MICROSTRUCTURE EVOLUTION DURING hot EXPANDING-EXTRUSION forming OF RESTRAINING RINGS

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Chinese Journal of Mechanical Engineering 1998年第2期11卷 62-66,72页

作者： Liu, Jiansheng Chen, Huiqin Guo, Huiguang Wu, Qingpei Taiyuan Heavy Machinery Inst China

A mathematic model for dynamic and static recrystallization of Mn18Cr18N steel is *** expanding extrusion forming and air cooling process of 600 MW retaining ring has been simulated by the combination of thermos coupled rigid viscoplasitic FEM with this model,and grain size distribution on cross section of ring is *** essential results can be provided for use of the new technique.

关键词： Retaining ring hot forming Microstructure evolution Finite element method

Discrete element and finite element coupling simulation and experiment of hot granule medium pressure forming

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Transactions of Nonferrous Metals Society of China 2015年第12期25卷 4089-4101页

作者：董国疆赵长财押媛媛赵建培燕山大学车辆与能源学院秦皇岛066004 燕山大学先进锻压成形技术与科学教育部重点实验室秦皇岛066004

The granule medium of discreteness is supposed to be continuous（Drucker-Prager model） in the existing finite element simulation analysis on the hot granule medium pressure forming（HGMF） process, so the granule medium may produce tensile stress in the process of pressure-transferring and flowing, which does not coincide with the reality. The analysis method, discrete element and finite element（DE-FE） coupling simulation, is proposed to solve the problem. The material parameters of simulation model are obtained by the pressure-transfer performance test of granule medium and the hot uniaxial tensile test of sheet metal. The DE-FE coupling simulation platform is established by adopting Visual Basic language. The features in the process that AA7075-T6 conical parts are formed by the HGMF process are analyzed and verified by the process test. The studies show that the results of DE-FE coupling simulation coincide well with the test results, which provides a new analysis method to solve the mechanics problem in the coupling of discrete and continuum.

关键词： granule medium aluminum alloy sheet hot forming finite element discrete element